Package org.HdrHistogram

Class DoubleRecorder

java.lang.Object

org.HdrHistogram.DoubleRecorder

All Implemented Interfaces:

DoubleValueRecorder

public class DoubleRecorder
extends Object
implements DoubleValueRecorder

Records floating point (double) values, and provides stable interval DoubleHistogram samples from live recorded data without interrupting or stalling active recording of values. Each interval histogram provided contains all value counts accumulated since the previous interval histogram was taken.

This pattern is commonly used in logging interval histogram information while recording is ongoing.

DoubleRecorder supports concurrent recordValue(double) or recordValueWithExpectedInterval(double, double) calls. Recording calls are wait-free on architectures that support atomic increment operations, and are lock-free on architectures that do not.

A common pattern for using a DoubleRecorder looks like this:

 DoubleRecorder recorder = new DoubleRecorder(2); // Two decimal point accuracy
 DoubleHistogram intervalHistogram = null;
 ...
 [start of some loop construct that periodically wants to grab an interval histogram]
   ...
   // Get interval histogram, recycling previous interval histogram:
   intervalHistogram = recorder.getIntervalHistogram(intervalHistogram);
   histogramLogWriter.outputIntervalHistogram(intervalHistogram);
   ...
 [end of loop construct]
 

Constructor Summary

Constructors

Constructor	Description
DoubleRecorder(int numberOfSignificantValueDigits)	Construct an auto-resizing DoubleRecorder using a precision stated as a number of significant decimal digits.
DoubleRecorder(long highestToLowestValueRatio, int numberOfSignificantValueDigits)	Construct a DoubleRecorder dynamic range of values to cover and a number of significant decimal digits.

Method Summary

Modifier and Type	Method	Description
DoubleHistogram	getIntervalHistogram()	Get a new instance of an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken.
DoubleHistogram	getIntervalHistogram(DoubleHistogram histogramToRecycle)	Get an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken.
DoubleHistogram	getIntervalHistogram(DoubleHistogram histogramToRecycle, boolean enforeContainingInstance)	Get an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken.
void	getIntervalHistogramInto(DoubleHistogram targetHistogram)	Place a copy of the value counts accumulated since accumulated (since the last interval histogram was taken) into targetHistogram.
void	recordValue(double value)	Record a value
void	recordValueWithCount(double value, long count)	Record a value in the histogram (adding to the value's current count)
void	recordValueWithExpectedInterval(double value, double expectedIntervalBetweenValueSamples)	Record a value
void	reset()	Reset any value counts accumulated thus far.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DoubleRecorder

public DoubleRecorder(int numberOfSignificantValueDigits)

Construct an auto-resizing DoubleRecorder using a precision stated as a number of significant decimal digits.

Parameters:

numberOfSignificantValueDigits - Specifies the precision to use. This is the number of significant decimal digits to which the histogram will maintain value resolution and separation. Must be a non-negative integer between 0 and 5.

DoubleRecorder

public DoubleRecorder(long highestToLowestValueRatio,
                      int numberOfSignificantValueDigits)

Construct a DoubleRecorder dynamic range of values to cover and a number of significant decimal digits.

Parameters:

highestToLowestValueRatio - specifies the dynamic range to use (as a ratio)

numberOfSignificantValueDigits - Specifies the precision to use. This is the number of significant decimal digits to which the histogram will maintain value resolution and separation. Must be a non-negative integer between 0 and 5.

Method Detail

recordValue

public void recordValue(double value)

Record a value

Specified by:

recordValue in interface DoubleValueRecorder

Parameters:

value - the value to record

Throws:

ArrayIndexOutOfBoundsException - (may throw) if value is exceeds highestTrackableValue

recordValueWithCount

public void recordValueWithCount(double value,
                                 long count)
                          throws ArrayIndexOutOfBoundsException

Record a value in the histogram (adding to the value's current count)

Specified by:

recordValueWithCount in interface DoubleValueRecorder

Parameters:

value - The value to be recorded

count - The number of occurrences of this value to record

Throws:

ArrayIndexOutOfBoundsException - (may throw) if value is exceeds highestTrackableValue

recordValueWithExpectedInterval

public void recordValueWithExpectedInterval(double value,
                                            double expectedIntervalBetweenValueSamples)
                                     throws ArrayIndexOutOfBoundsException

Record a value

To compensate for the loss of sampled values when a recorded value is larger than the expected interval between value samples, Histogram will auto-generate an additional series of decreasingly-smaller (down to the expectedIntervalBetweenValueSamples) value records.

See related notes DoubleHistogram.recordValueWithExpectedInterval(double, double) for more explanations about coordinated omission and expected interval correction. *

Specified by:

recordValueWithExpectedInterval in interface DoubleValueRecorder

Parameters:

value - The value to record

expectedIntervalBetweenValueSamples - If expectedIntervalBetweenValueSamples is larger than 0, add auto-generated value records as appropriate if value is larger than expectedIntervalBetweenValueSamples

Throws:

ArrayIndexOutOfBoundsException - (may throw) if value is exceeds highestTrackableValue

getIntervalHistogram

public DoubleHistogram getIntervalHistogram()

Get a new instance of an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken.

Calling getIntervalHistogram() will reset the value counts, and start accumulating value counts for the next interval.

Returns:

a histogram containing the value counts accumulated since the last interval histogram was taken.

getIntervalHistogram

public DoubleHistogram getIntervalHistogram(DoubleHistogram histogramToRecycle)

Get an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken.

getIntervalHistogram(histogramToRecycle) accepts a previously returned interval histogram that can be recycled internally to avoid allocation and content copying operations, and is therefore significantly more efficient for repeated use than getIntervalHistogram() and getIntervalHistogramInto(). The provided histogramToRecycle must be either be null or an interval histogram returned by a previous call to getIntervalHistogram(histogramToRecycle) or getIntervalHistogram().

NOTE: The caller is responsible for not recycling the same returned interval histogram more than once. If the same interval histogram instance is recycled more than once, behavior is undefined.

Calling getIntervalHistogram(histogramToRecycle) will reset the value counts, and start accumulating value counts for the next interval

Parameters:

histogramToRecycle - a previously returned interval histogram (from this instance of DoubleRecorder) that may be recycled to avoid allocation and copy operations.

Returns:

a histogram containing the value counts accumulated since the last interval histogram was taken.

getIntervalHistogram

public DoubleHistogram getIntervalHistogram(DoubleHistogram histogramToRecycle,
                                            boolean enforeContainingInstance)

Get an interval histogram, which will include a stable, consistent view of all value counts accumulated since the last interval histogram was taken.

getIntervalHistogram(histogramToRecycle) accepts a previously returned interval histogram that can be recycled internally to avoid allocation and content copying operations, and is therefore significantly more efficient for repeated use than getIntervalHistogram() and getIntervalHistogramInto(). The provided histogramToRecycle must be either be null or an interval histogram returned by a previous call to getIntervalHistogram(histogramToRecycle) or getIntervalHistogram().

NOTE: The caller is responsible for not recycling the same returned interval histogram more than once. If the same interval histogram instance is recycled more than once, behavior is undefined.

Calling getIntervalHistogram(histogramToRecycle) will reset the value counts, and start accumulating value counts for the next interval

Parameters:

histogramToRecycle - a previously returned interval histogram that may be recycled to avoid allocation and copy operations.

enforeContainingInstance - if true, will only allow recycling of histograms previously returned from this instance of DoubleRecorder. If false, will allow recycling histograms previously returned by other instances of DoubleRecorder.

Returns:

a histogram containing the value counts accumulated since the last interval histogram was taken.

getIntervalHistogramInto

public void getIntervalHistogramInto(DoubleHistogram targetHistogram)

Place a copy of the value counts accumulated since accumulated (since the last interval histogram was taken) into targetHistogram. Calling getIntervalHistogramInto(org.HdrHistogram.DoubleHistogram)() will reset the value counts, and start accumulating value counts for the next interval.

Parameters:

targetHistogram - the histogram into which the interval histogram's data should be copied

reset

public void reset()

Reset any value counts accumulated thus far.

Specified by:

reset in interface DoubleValueRecorder